1. Field of the Invention
This invention relates to a timepiece device for indicating the time, and more particularly to an improved illumination inside and outside the timepiece.
2. Description of the Prior Art
In a conventional comparatively large timepiece such as a wall clock and a table clock, there is provided a large dial to read the time, wherein it is possible to have comparatively free choice of a time indicating means or a dial illuminating means and for example, when an electric light segment display is used, it is possible to easily read the time even in the dark or from a distance. Also, in a timepiece of a digital display type using a liquid crystal display (hereinafter referred to as "LCD"), it is necessary to make the backlight put on to read the time in the dark.
Also, U.S. Pat. No. 4,775,964 entitled "Electroluminescent Dial For An Analog Watch And Process For Making" discloses an analog watch in which a dial is illuminated, by using an electroluminescent device (hereinafter referred to as "EL"), to enable reading the time in the dark.
As described above, it is known in the conventional timepiece that the LCD having the backlight, a light-emitting diode (hereinafter referred to as "LED") or the like is used as a time indicating means to enable reading the time in the dark and also as an illuminating means to illuminate the dial.
However, in the conventional timepiece, there is only provided an electrically light-emitting means which can produce a quantity of light in such an amount as to make it easy to read the time. The quantity of light is insufficient to illuminate an outside object. Accordingly, the electrically light-emitting means is not sufficient to serve for, for example, as a flashlight in case of searching for a keyhole in the dark.
It may be however possible in the timepiece provided with the EL to make an object to be illuminated visible to a certain extent by bringing the side of the dial near such object, but it is still not enough to produce sufficient light from the timepiece.
To drive the EL, it is necessary to convert a direct-current voltage of a cell built in the time piece to an alternating voltage through an inverter and supply the power to the EL. Exemplary patent specifications showing the driving circuit for the EL are seen in Japanese patent publication No. Sho. 62-15032 and U.S. Pat. No. 4,527,096.
When the EL is used for illuminating the dial, an illumination effect can not be obtained in practice if the EL is off in a moment after it is on. In this case, it is necessary to provide, for example, a timer function in the driving circuit which is adapted to maintain the "on" condition for a given period of time after an on/off switch for the EL is set.